The present invention generally relates to tamper-evident induction foil liners for sealing containers. The present invention more specifically relates to an improved tamper-evident induction foil liner which provides an enhanced water vapor barrier.
Tamper-evident liners are common for sealing containers, for example, bottles containing drugs or food. Such liners are especially useful because they prevent or warn of tampering with a containers contents.
To facilitate user-friendly liner removal, liners are often provided with an integral pull-tab which may be gripped by a person's fingers. One such type of pull-tab is formed by a portion of the foil disk seal which extends over the outer diameter of the container. The tab can be pulled upward and across the container opening to peel the foil disk from the container lip. A pull-tab liner of that type is disclose in U.S. Pat. No. 5,197,618, to Goth, which is incorporated herein by reference. That patent discloses a pull-tab liner structure and suitable materials for a fusion peelable-bond induction foil liner which is removed cleanly and easily from a container lip.
Referring to the Figures, a prior art liner 10 of the type disclosed in U.S. Pat. No. 5,197,618 is illustrated in FIGS. 1, 1A and 4. The prior art liner 10 consists of four stacked layers A, B, C and D. A first layer A is a peelable polymer layer which may be fusion-bonded to a lip defining an opening of a container 14. A second layer is a low cohesive strength layer B, disposed against the polymer layer A. A third layer is a foil layer C disposed against layer B on a side opposite the low cohesive strength layer A. A fourth layer is a tear-resistant backing layer D disposed on top of the foil layer C.
In certain applications, it is desirable that a pull-tab container liner minimizes or prevents the migration of moisture into a container interior. For example, dampness or humidity can damage or negatively affect various goods. Also, moisture migration out of a container is undesirable, as it may result in the drawing out of a product over an extended period. Unfortunately, many known induction foil liners, including that disclosed in afore-mentioned U.S. Pat. No. 5,197,618, permit an undesirable amount of moisture migration.
Therefore, it is an object of the present invention to provide an improved tamper-evident foil induction liner which reduces or prevents water vapor migration.